One conventional approach for connecting integrated circuit (IC) chips (or, die) to a larger substrate (or, wafer) is to use ball grid array (BGA) interconnects, also referred to as solder ball (or solder bump) packaging. This interconnect packaging utilizes solder balls to form both physical and electrical connections between the IC chip and the substrate. The BGA interconnect packaging further includes an underfill material which surrounds the solder balls and sits between the chip and the substrate. The underfill material is conventionally flowed in around and in between the solder balls to fill spaces created by the separated solder balls which connect the chip and substrate. This underfill material conventionally forms a supportive matrix which helps to prevent solder fatigue or wear-out, and improves the long-term reliability of the BGA interconnect.
However, these conventional BGA interconnect structures experience several problems. In some cases, the BGA interconnects experience “solder extrusion”, where reflowed solder used to form the BGA interconnect exerts an outward pressure on the underfill material, in particular, at the interface of the underfill material and the polyimide layer on the chip. This pressure can degrade the bond between the underfill material and the chip (via the polyimide layer), and can further delaminate the underfill material proximate the interface of the underfill and the chip.